Godsmack frontman Sully Erna has blamed his recent vocal problems on the exhaustion of touring.The rock group was forced to cancel the remaining dates of its summer (12) European tour after Erna fell sick with a throat infection, but they were back on stage on Friday (17Aug12) to kick off the Rockstar Energy Uproar Festival in Kansas. Erna insists he has recovered from the problems which blighted their previous shows, and he admits fatigue from constant travelling was to blame for his illness. He tells The Pulse Of Radio, "It was actually a bit of an infection that I had in the back of my throat, and I was exhausted, I hadn't slept in three days when we got to Europe, and it was just a combination of being like really tired, singing exhausted and (I) just pushed myself a little too hard. "And I injured it (throat) enough that I had to kind of shut it down, but it wasn't like a permanent injury or something like that. It was the first and only time it's ever happened in my career, and I don't expect this to become a habit."